orig_filename ="pride_and_prejudice.backup.txt"
target_filename ="pride_and_prejudice.txt"
with open(orig_filename) as read_file:
    raw_text = read_file.read()
text=[
    character.lower()
    for character in raw_text
    if( ord(character)>=ord('a')  and ord(character)<=ord('z'))
    or character==" "
    or character=="\n"
    or (ord(character)>=ord('A') and ord(character)<=ord('Z'))
]
with open(target_filename,"w") as write_file:
    write_file.write("".join(text))